It is known in the art to cut a seed furrow with an upright shank or knife and simultaneously fluff the furrow sidewalls with laterally projecting wings while placing fertilizer in an offset manner along the seed line of the furrow. See for example U.S. Pat. No. 5,495,814 to David R. Primus titled Sub-zone Tiller with Offset Fertilizer Placement.
However, in the Primus tiller fertilizer is applied through a transversely extending cross tube at the rear of the device that has a pair of discharge openings at its opposite ends. In some soil conditions, these openings can become plugged, making it difficult to accurately and consistently apply proper amounts of fertilizer. Moreover, the discharge tube is exposed to wear from abrasive soil, which shortens its useful life. In addition, an upwardly inclined rear portion on the wings just ahead of the discharge tube does not provide the optimum soil flow and lifting action as the unit moves through the subsoil, and such portion is subject to premature wear.
The present invention provides a subsoil applicator and furrow loosening device that minimizes the opportunities for plugging the discharge outlets and reduces the opportunities for premature wear of the fertilizer delivery structure. It also enhances soil flow and achieves improved loosening or fluffing action while at the same time having greater resistance to premature wear.
In one preferred embodiment of the invention, the applicator has the fertilizer delivery structure housed internally within the shank and wings of the device, with the wings having laterally offset and rearwardly facing discharge outlets through which the fertilizer passes out of the device and into the soil. A thickened rear portion of the wings presents a generally upright rear wall within which the discharge outlets are disposed. The rear wall has an upper overhanging portion and a lower undercut portion to present a recess, the outlets being disposed primarily in such recess so as to reduce clogging and encourage free discharge of fertilizer from the unit.
The thickened rear portion of the wings also presents a transversely extending rearmost boss that is raised with respect to forward portions of the wings. Each boss has a convexly curved, generally upwardly facing top surface that promotes streamlined soil flow and increases the wear characteristics of the wings, particularly in the critical rear portions thereof where the tubular fertilizer passages are located.